Spectrum approach, flaw

The flaw spectrum approach may be capable also of correlating failure data obtained under conditions which appear to give different material behavior. For example, tensile, Izod, and dart drop impact tests all give different impact energies or toughness measures. In part, this may be explained by the simple idea that a different fraction of flaws is active in each test. Equal biaxial loading (as in dart drop) and uniaxial tension (as in tensile impact) give rise to different flaw activities thus it is to be expected that the number of crazes produced in each test will be different. 

We have intended to demonstrate that a flaw spectrum analysis presents a plausible and useful approach to the problem of multiple flaw failure phenomena in solid polymers. Effects of orientation and stress state may be explained by such an approach, but much additional theory and experiments are required to establish the validity of the method. Several obvious shortcomings of the theory can be overcome, in principle, by a more rigorous analysis. The more serious assumptions or limitations which we intend to either remove or justify in future work are as follows. 

The fracture mechanics approach to bond failure considers crack initiation and propagation, arising from flaws inherently present in the bondline. The probabilistic nature of failure can be incorporated into this theory by assuming a flaw spectrum.A population is defined in terms of a distribution of flaw sizes, shapes, and orientations. A statistical treatment of fatigue life has also been reported, using a Monte Carlo method to introduce randomness into the crack propagation mode. ... 

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